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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.


Monday, June 13, 2022

SPC Jun 13, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0317 PM CDT Mon Jun 13 2022 Valid 132000Z - 141200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF FAR SOUTHERN LOWER MICHIGAN INTO NORTHEAST INDIANA AND WESTERN OHIO... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe thunderstorms are expected across parts of the northern Plains, and from portions of the Midwest into the Great Lakes and Ohio Valley. Large hail, damaging winds, and a few tornadoes are possible. Some of the winds could be significantly severe (75+ mph) across parts of the Midwest/Ohio Valley this afternoon and tonight. ...20Z Update... Portions of the Ohio Valley have been upgraded to a Moderate Risk for the anticipation of a highly organized MCS/possible Derecho developing from a supercell structure across southern WI. Despite the lack of agreement in high-resolution guidance, this supercell is traversing a strong buoyancy gradient (with extreme MLCAPE values exceeding 5000 J/kg noted in the OH Valley). In addition, 40+ kts of effective bulk shear are also present along the buoyancy gradient, which expands across a long west-east corridor over northern portions of the OH Valley. Expectations are for this supercell (which already shows an intense RFD surge per latest KMKX radar data) to eventually become more outflow dominant, generating a strong cold pool preceded by the extreme instability. Upscale growth with the cold pool would support an expanding MCS traversing a CAPE/shear parameter space typically associated with bow echoes/derechoes. In addition, multicells continue to percolate across central IN amid an extremely unstable environment (i.e. 5000+ J/kg MLCAPE per 18Z mesoanalysis) and an appreciable severe wind threat could develop with this cluster as well should upscale growth occur. A significant wind area has been added to portions of the Slight Risk across portions of central into northern South Dakota. Here, the potential exists for an HP supercell/short bowing segment to manifest from earlier storms along or immediately behind the surface cold front somewhere within the 03-06Z period (especially in the 12-18Z runs of the HRRR) and traverse an axis of high-end elevated buoyancy (i.e. 4000 J/kg MUCAPE driven by 9 C/km deep-layer lapse rates). Should this scenario unfold, 75+ mph gusts may occur in addition to 2+ inch hail. Consideration was considered for an upgrade to a Category 3/Enhanced. However, the localized nature/expected limited coverage of the higher-end severe threat precludes an upgrade. Please see MCD #1144 for short-term severe concerns across the northern Plains. ..Squitieri.. 06/13/2022 .PREV DISCUSSION... /ISSUED 1204 PM CDT Mon Jun 13 2022/ ...Midwest/Great Lakes... A consequential potential for impactful storms exists today into tonight across the region, potentially including long-lived/intense MCS development, owing to a high degree of moisture and extreme potential instability. However, short-term uncertainty remains high regarding spatial details exists owing to a strong capping inversion, along with guidance variability in terms of timing/spatial differences. Multiple MCVs, albeit generally weakening, are still readily apparent at late morning across portions of Iowa/southern Minnesota into western Wisconsin. Regional WSR-88D VWP data features notably enhanced mid-level winds, particularly by mid-June standards, within this same regional corridor (for example, 50-60 kt winds 3-6 km AGL recently noted at KDMX/Des Moines). 12z upper-air analysis in conjunction with more contemporary GPS PW values reflects a moisture-rich corridor particularly from eastern Iowa and much of Illinois southeastward into southern Indiana. A considerable elevated mixed layer extends east-northeastward atop this moisture, highlighted by a 14.6 C temperature at 700 mb per 12z ILX/Lincoln, IL observed sounding. Given the notable mid-level warmth, storm development later this afternoon into evening will tend to favor areas near/immediate cool side of a northward-shifting warm front across the region. This would favor development across southern Wisconsin into northern Indiana/Lower Michigan and Ohio. One potential exception could be across downstate areas of eastern Illinois into Indiana, where glancing MCV-related ascent (reference ongoing mid-level convection near/west of the Mississippi River this morning) could interact with a very moist/unstable and weakly inhibited boundary layer downstream highlighted by surface dewpoints generally in the upper 70s F. Where storms do regionally develop, large hail and damaging winds can be expected, along with at least some potential for tornadoes with surface-based storms developing near/interacting with the warm front. An upgrade to Moderate Risk may still be warranted across parts of the region (particularly Lower Michigan, northern Indiana and/or Ohio) pending subsequent observational trends and increased confidence in a preferred sub-regional corridor of intense storm development. ...Dakotas... Influenced by the approaching upstream upper trough, a surface low is forecast to deepen over eastern Wyoming this afternoon while a cold front moves across the northern Rockies and High Plains. Thunderstorms are expected to form along the front by early evening over western South Dakota/North Dakota and track northeastward. Vertical shear profiles will be favorable for supercell storms capable of all hazards, particularly along and on the immediate cool side of the boundary. ...Southern/central High Plains... Modest moisture and a hot/deeply mixed boundary layer could support a few severe-caliber wind gusts if/where storms develop late this afternoon/early evening. ...Maine... Influenced by modest buoyancy and moderately strong winds aloft on the periphery of an upper low over Quebec, a few strong to severe thunderstorms may occur this afternoon across the region. Read more CHECK UPDATE ZOOM GRAPHIC
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